Hydraulic load compensating snubber



Nov. 3, 1964 H. c. zlNTz lawn. 3,155,198

HYDRAULIC LOAD CQMPENSATING SNUBBER I Filed Jan. 3l, 1963 4 Sheets-Sheet 1 FIG.,

Afraifviff Nov. 3, 1964 H. c. zlNTz ETAL 3,155,198

HYDRAULIC LOAD COMPENSATING SNUBBER Filed Jan. 5l, 1965 4 Sheets-Sheet 2 l /23 (37 i2 5 Y /27 l 92 92 y.iniii'I INVENTOR5 4free/vin# v Nov. 3, 1964 H. c. zlN-rz ETAL. 3,155,198

HYDRAULIC LOAD COMPENSATING SNUBBER Filed Jan. 3l, 1963 4 Shee'cs-Sheei'l 5 Nov. 3, 1964 H. c. ZIN-rz ETAL 3,155,198

HYDRAULIC LOAD coMPENsATxNG sNuBBER Filed Jan. 51, 1963 v 4 Sheets-Sheet 4 INVENToRs ab* Hon/ipp C.' Z/Nfz w/Luea D, chf/ws x Army/vir.;

United States Patent O M' 3,155,198 HYDRAULHC 'LGAD CGMPENSATNG SNUBBER Howard Q. Zintz, Walnut Creek, and Willard D. Chiids, Concord, Calii., assignors to The Rucker Company Filed Jari. 31, 14;63, Ser. No. 255,405 11 Claims. (Cl. 18S-97) Our invention relates to means for controlling the motion of relatively movable bodies and has especially to do with arrangements in which the relative motion of the bodies is carefully controlled despite variations in the forces imposed thereon.

In certain ields, particularly in the iield of radio astronomy, for example, there is employed a relatively large antenna in the form of a bowl or dish mounted on pivotal structures so that the antenna can be moved with respect to its mounting structure in various ways. While the antenna has a relatively large angularity of motion, its total travel is nevertheless limited. The antenna is exposed to the vagaries of the weather, particularly high winds, and is otherwise subjected to various forces not always precisely known in advance and no't always promptly controllable.

In the event an antenna movement is permitted to get out of control or if the antenna comes to the end of its path suddenly, a great deal of damage may be done not only to the antenna itself but also to at'tendant, precise machinery.

It is therefore an object of our invention to provide a hydraulic load compensating snubber to control the relative motion between bodies, for example, between an antenna and its support or base.

Another object of the invention is to provide mechanism for use with an antenna'eiective to control the antenna motion to prevent undue or damaging forces thereon.

Another object of the invention is to provide a simple, reliable structure for preventing damage to relatively movable members.

Another object of the invention is to provide a structure which assists in damping or controlling the movement of relatively movable members subjected to variable forces.

Another object of the invention is to provide an improved hydraulic load compensating snubber.

A still further object of the invention is to provide an improved antenna controlling mechanism.

A further object is to provide a hydraulic mechanism in the form of a package or assembly that can be easily included with relatively movable parts of various sorts to control their relative motion.

Other objects together with the foregoing are attained in the embodiment of the invention described in the accompanying description and illustrated in the accompanying drawings, in which:

FlGURE 1 is a side elevation of an antenna mechanism on its support with the hydraulic load compensating snubber of our invention connected thereto;

FIGURE 2 is a cross section, the plane of which is indicated by the line 2 2 of FIGURE l;

FIGURE 3 is a pian oi an embodiment of the hydraulic load compensating snubber;

FIGURE 4 is a side elevation of the snubber unit iilustrated in FIGURE 3;

FIGURE 5 is a view similar to FIGURE 4, but is broken away in various areas to show in cross section the terior detailed construction or" the snubber unit; and

FIGURE 6 is a diagrammatic illustration of the hydraulic load compensating snubber, particularly with respect to the hydraulic circuitry thereof.

' In its preferred form the hydraulic load compensating snubber is applicable to many diierent installations where- 3,l55,l98 Patentedv Nov. 3, 1964 in one body moves relativeiy to the other, especially under the inuence of random or variant forces. The device has achieved commercial success in a radio telescope ernploying a mounting structure and a dish antenna. It is described as an example in that environment.

The antenna structure of the radio telescope includes a base 6 or frame mounted on the ground and carrying a pair of uprights 7 and 8 to provide pivotal mountings 9 and 11. These support a cradle 12 for rotation or pivotal movement about a primary, horizontal axis 13. The cradle 12 is provided with a pair of journals 14 and 16 carrying a trunnion frame 17 for pivotal or rotational movement about a secondary axis 18 normal to and intersecting the primary axis 13. Extending upwardly from the trunnion frame 17 is a support yoke 19 to which an antenna dish 2t) is secured. Various mechanisms, not shown, are utilized for rotating the dish 20 about :the axis 18 through a path having xed limits and further mechanisms are provided for rotating the dish 20 about the axis 13 through a limited angular travel. The mechanisms for moving the antenna dish are relatively low in power and are precise under usual conditions but are not always in full control of the antenna motion especially under hand operation and when sudden large forces are externally applied.

Pursuant to our invention, a hydraulic load compensating snubber 2i is installed between the frame 6 and the cradle 12 and a pair of similar hydraulic load compensating snubbers 22 and 23 are installed between the yoke 19 and the cradle 12, Since the hydraulic load compensating snuobers are all identical, the following description applies equally to all of them.

As particularly shown in FIGURES 3 and 4, the hydraulic mechanism interconnecting the frame 6 and the crade 12, for example, includes a hydraulic variable enclosure 31. rl`his is made up of an external cylinder 32 at one end carrying wings 33 having openings 34 to receive the mounting pivot for the variable enclosure. The cylinder at both ends is substantially closed by heads 36 and 37. The interior of the cylinder is divided into a primary chamber 38 and a secondary chamber 39 by means of an intervening piston 41 mounted at one end of a piston rod 42, This projects through the head 37 and has a terminal 43 for appropriate attachment to the other of the relatively moving bodies. The hydraulic variable enclosure 31 is so mounted that there is a full stroke of the piston i1 within the cylinder when the antenna goes through either half of its maximum rotary excursion or pivotal rotation. When the antenna is near-or at the inidpoint of 'its travel, the volume of the primary chamber 3S 1s a mmimum.

Pursuant to the invention, means are provided for controlling the excursions of the piston 41 within the cylinder 32 correspondingly to control the antenna dish. For that reason, the iirst chamber 38 is connected by a first conduit Sti to a control unit 51 conveniently mounted on the cylinder 32. The irst conduit 50 includes a number of parts and extends from the first chamber 38 to a flow control valve 52. This valve (diagrammatically shown in FIGURE 6) controls the amount of fluid passing therethrough in a given time in accordance with diterential of pressures exerted on the opposite ends of :a movable member or shuttle 53 within the valve. Flow from the ilow control valve in the first conduitStl then is through a restricting oriiice 54 and continues at least partly through a shunt pipe 56 to a dow line 57 extending to one end of the control unit 51.

The secondary chamber 39 is also connected to the control unit but through a second conduit 61 which incorporates a number of connections and includes a junction pipe 62 joined to a pipe 63 extending to the other end of the control unit 51.

The control unit, particularly as shown in FIGURE 5, is a casing o6 enclosing a compartment 67 of annular form partly defined by a concentric cylinder shell 68. At one end the shell is appropriately sealed and is piloted into a reduced portion of the casing d6 and at the other end the cylinder shell 63 is mounted on a central boss 69 incorporated in a closure head 71 on the casing. The cylinder shell is divided into a third chamber 72 and a fourth chamber 73 by means of an elongated piston 74 which is free oating.

The piston 74 is normally urged in a direction to make the third chamber 72 have a minimum volume. This is accomplished by a pair of concentric helical coil springs 78 and 79 at one end resting against the head of the piston 7d and at the other end resting against the closure head 71. Travel of the piston to reduce the volume of the fourth chamber 73 is limited by a tubular stop 81 seated in the closure head 71 and extending for an appropriate distance to be contacted by the piston head at the end of its stroke.

The piston 74 is particularly provided with a circumferentially extending land S2 which in traversing the cylinder shell d progressively covers and blocks successive ones of a series of openings S3 and S-i spaced apart axially in the cylinder shell and when open aifording communication between the compartment 67 and the fourth chamber 73.

The flow line 57 forming part of the iirst conduit 5@ extends appropriately into the casing 66 and opens directly into the third chamber 72 opposite to the head of the piston 74. The second conduit 61, by means of the pipe portions 62 and 63 thereof enters the fourth chamber 73 through the tubular stop S1. Thus the control piston 74 on its opposite sides is subjected to the pressures on the opposite sides of the piston 41 as modied by Various of the interposed control devices.

Means are provided vin the iirst conduit :'ii for blocking ow therethrough. At an appropriate location, hydraulically downstream of the orifice 54 and physically on the casing 66, there is disposed a pair of shiftable valves 91 and 92, each of which has two extreme positions. In one of these positions ow through the valve 91 and continuously through the first conduit Sil-57 is permitted, whereas in the other position of the valve low is blocked and cannot continue through the iirst conduit Sil. In the position of the valve 91 shown, an extension pipe 93 leads to a through passage 94 in the valve connected by a pipe 96 to the line 57. Another through passage 97 in the valve is connected by pipes 98 and 99 to the first conduit Sil on the other side of the valves. The valve 91 is normally urged into the position shown in FIGURE 6 by a spring 161.

The spring is overcome by a solenoid 102 when the solenoid is energized and the valve core is shifted so that a pair of cross bores 163 and 1134 come into operation. These cross connect the pipes 96 and 98 as well as the pipes 93 and 99. In the parallel connection position shown in FIGURE 6, iow from the primary part ot' the first conduit 50 into the secondary part ofthe rst conduit 59 is blocked and cannot occur. When, however, the solevnoid1t`2 is energized to overcome the spring 101 and to shift the valve core, then the cross connection allows flow from the primary part of the lirst conduit t) into the secondary portion thereof.

Since the valves 91 and 92 have considerable resistance to llow, and since it is desired to reduce the ilow resistance in this portion of the circuit, the valve 92 is arranged in parallel with the valve 91. It is provided with pipes 106 and 107 leading to one cross connected portion of the valve and pipes 108 and 1t9 leading to the other cross connected portion thereof. The pipes 166 and 197 are joined to the primary part of the iirst conduit 51B and the pipes 168 and 109 are connected to the secondary part of the irst conduit Sil. The Valve 92, like the valve 9 1, has a spring 111 urging it in one direction and a solenoid 112 which, when energized, overcomes the force of the spring and shifts the valve to its other position. As Shown in FIGURE 6, the valve 92 is in blocked location so that it does not permit flow from the primary portion to the secondary portion of the first conduit Sil, whereas in its shifted position flow from the primary portion to the secondary portion of the' rst conduit is permitted.

In the antenna dish and frame structure, a limit switch 113 (FIGURE 1) or the like is usually provided at a convenient location. The switch is actuated by the antenna dish 19 approaching one of its extreme positions. The limit switch 113 is connected in an electric circuit in which the solenoids 102 and 112 are also connected in series. Thus, under normal circumstances the valves 91 and 92 are held by the energized solenoids in open or permitting position and there is little resistance to hydraulic ilow. But when the solenoids are cle-energized, the valves are spring shifted simultaneously and flow therethrough 4is blocked or prevented. ln an actual installation there can be more than one limit switch and also a manual switch, if desired.

The mounting of the snubber structure (FIGURES 1 and 2), particularly of the hydraulic variable enclosure 31, is such that the two pivotal axes 114 and 115 or the variable enclosure are in one position in alignment with the pivot axis 13 of the structure. When the structure swings either side of this intermediate position, the piston rod 42 extends from the cylinder 32. In practice, when the piston rod is moved inwardly of the cylinder as the antenna dish is being driven through the initial portion of its motion away from one end of its path, the valves 91 and 92 are in open position and ailord little, if any, restriction to free antenna operation. However, as the jack 31 passes through and beyond its center position with the three pivotal axes in alignment, then the piston rod 42 is withdrawn from the cylinder. This motion 'also is freely accomplished since the valves 91 and 92 may still remain open.

When, however, a limit switch is actuated or when the electrical circuit to `the solenoids 102 and 112 is manually or otherwise de-energized, then the valves 91 and 92 are closed. There can no longer be any more flow between the primary portion of the rst conduit 56 and the secondary portion thereof. But there being continued outward movement of the piston rod 42, hydraulic Huid expelled through the primary por-tion of the rst conduit 50 .travels through the flow control valve 52 and through the oriiice S4 and then transfers through the shunt pipe 55 and through the open passage M- of the valve 91 and then into the line 57 from which it travels to the third chamber 72. The incoming tluid displaces the piston 74 to the right in FIGURE 6 and to the left in FIGURE 5 against the urgency of the springs 7S and 79. The resulting motion of the piston 74- then reduces the volume of the fourth chamber 73. But the contained hydraulic fluid is `blocked from owing through the pipe 63 because a check valve 116 is interposed therein. The `only escape for the hydraulic iluid from the fourth chamber 73 is through the uncovered openings 83 and 84 into the compartment 67.

From the compartment 67 ow occurs through a connecting pipe 117 (FIGURE 6) tothe pipe 62 and to the second conduit 61 back to the secondary chamberV 39. The pressure of the fluid in the compartment 67 is transmitted through a connecting'conduit 11S to one side of Ithe dow control valve 52. As the piston 74 is displaced, the pressure in the conduit 118 increases and Iis exerted on the shuttle 53 of the flow control valve` in addition to the usual pressure of la spring 119 thereon. Pressure from the lconduit 118 is diierentiated from the pressure in the rst conduit 56 upstream' ofthe orifice 54 since a pipe 121 in the first conduit is looped to connect with the opposite end of the shuttle 53. Thus the shuttle 5d is momentarily positioned as a result of the dilerential pressure existing in the first conduit this increases the differential pressure on the flow control valve 52 and tends to throttle or shut such valve. This in turn increasingly restricts the flow from the first compartment 38 and tends to arrest or decelerate the outward motion of the piston rod. The faster the rnotion of the piston rod tends to be, the greater the differentia-l pressure on the flow control valve and the more the outgoing piston rod is retarded. The maximum rate of motion is therefore pre-established despite high forces. if by any chance the pressure should become greatly excessive in .the primary portion of the first conduit 5G, then such excess pressure is relieved through a pipe 122 in which a relief valve 123 is situated. This discharges through a pipe 124 connected to the pipe 117. The relief valve 123 is set at a pressure sufficiently high so that it opens only under emergency conditions. Normally, pressure fluctuations suiiicient for designed operation of the system are insuiiicient to open the relief valve.

As the piston 74 continues to decrease the volume of the fourth chamber 73, .the land S2 overrides the lirst opening 83 and thus cuts down the -area for hydraulic efflux. This produces an increase in pressure within the compartment 67, slows the piston movement, and increases the differential pressure on .the ow con-trol valve, thus closing it further. As the piston '74 continues its travel, more of the openings Sd are closed off, the piston is slowed and the control valve 52 is nearly closed. When the piston 74 gets near the end of its stroke and the springs 78 and 79 are compressed nearly to their maximum amounts, there is virtually no efiiux into the compartment 67 so that the piston 74 is virtually stopped. Correspondingly, the projection of the piston rod is almost stopped.

While the volume of the fourth chamber 73 is being reduced, a quantity of hydraulic fluid is displaced from the control unit and must also be taken into account. Fluid in the line 117 has access through the pipe 62 and through the secondary portion of the primary conduit 5t? and through a duct 126 to an accumulator 12.7. The accumulator generally iioats on the hydraulic lines at a predetermined nominal pressure, for example, two hundred pounds per square inch. The accumulator accepts excess hydraulic fluid when the volume of the remainder of the system decreases and supplies fluid when the volume of the remainder of the system increases.

As the control unit piston 74 changes its position more and more to decrease the volume of the fourth chamber 73, the extension movement of the piston rod 4t2 is gradually decelerated and is finally stopped. The piston rod o-r variable enclosure motion takes place at a rate governed by the control unit and without regard to the magnitude of the excess or random force which may be exerted on the antenna dish. Sudden gusts of wind, for example, do not produce any unusual movements of the antenna dish near the ends of its path. The antenna dish is always halted gradually and at a controlled rate and cannot abruptly strike any part of its associated structure.

When the antenna dish motion is reversed, Vthe piston rod 42 retreats into the cylinder 32 and the piston 41 moves to enlarge the rst chamber 38 and to diminish the second chamber 39. Hydraulic fluid is discharged from the chamber 39 through the second conduit 61 to the accumulator' 127 while hydraulic fluid is admitted to the chamber 38 through the primary portion of the first conduit 50, this hydraulic fluid being taken from various sources. For example, since the piston 74 is being restored to its original location by the springs 7S and 79, fluid ows from th third chamber 72 through the line 57 and through the first conduit Sti to the chamber 38. Additionally, fluid from the accumulator 12:7 can travel from the duct 126 'through the secondary portion of the first conduit S0, thence through the pipe 117 and through a bypass check valve 1%, thence :through a return pipe 129 to the primary portion of the first conduit 50 to the chamber 38. There is consequently no possibility of a rapidly enlarging rst chamber 38 being liuid starved. During the inward motion of the piston rod the valves 91 and 92 are normally in their open position, but even if they should be in their blocked position, this is not important during contraction of the variable enclosure 31 since there is adequate return flow through alternate or parallel paths to permit the parts to be promptly moved.

By varying the size, number and location of the openings 83 and 84 in the cylinder sleeve 68, the rate of motion of the structure during particular portions of travel or the amount of damping or control of the motion can be varied to meet any particular specification. It is usual to program the structure so that near the end of the motion of the antenna dishrthe rate of deceleration (negative acceleration) is constant, for example, five degrees per second. The orifice 54 is usually calibrated so that even without the influence of the remaining part of the restraining structure the hydraulic flow is restricted so that the maximum velocity of the antenna dish will not exceed a set value, for example, six degrees per second.

Pursuant to the invention, therefore, we have provided a hydraulicy load compensating snubber which can readily be applied to an appropriately driven movable member on a base in such a fashion that there is no possibility of the structure being moved by vagrant forces into a dangerous or destructive position, but in which the restraint and deceleration of the structure are sufficient to afford proper control and positioning without restricting the motion in a direction away from an end point.

What is claimed is:

1. A hydraulic load compensating snubber comprising a hydraulic variable enclosure including a first cylinder closed at both ends and having a first piston therein dividing said first cylinder into a first chamber and a second chamber and having a piston rod onsaid piston extending through one of said ends, a control unit including a second cylinder closed at both ends and having a second piston therein dividing said second cylinder into a third chamber and a fourth chamber, a first conduit extending between said first chamber and said third chamber, a second conduit extending between said second chamber and said fourth chamber, a hydraulic connector between said first conduit and said second conduit, a control means movable between one position permitting liow through said connector and another position blocking flow through said connector, and a ow control valve in said first conduit responsive to the difference in pressure between said third chamber and said fourth chamber.

2. A hydraulic load compensating snubber comprising a hydraulic variable enclosure including a first cylinder closed at both ends and having a first piston therein dividing said first cylinder into a first chamber and a second chamber, a control unit including a second cylinder closed at both ends and having a second piston therein dividing said second cylinder into a third chamber and a fourth chamber, a first conduit extending between said first charnber and said third chamber, a second conduit extending between said second chamber and said fourth chamber, a hydraulic connector between said first conduit and said second conduit, a valve in said connector movable between open position and closed position, a restricting orifice in said first conduit, a flow control valve in said first conduit, means for subjecting said flow control valve to pressure in said first conduit between said first chamber and said orifice, and means for subjecting said flow control valve to pressure in said fourth chamber.

3. A hydraulic load compensating snubber as in claim l in which said second piston is mechanically urged to educe the volume of said third chamber.`

4. A hydraulic load compensating snubber as in claim l in which said second cylinder is provided with a plurality of openings for establishing communication between said fourth chamber and said second conduit and in which said second piston in moving successively overlies and blocks said openings.

5. A hydraulic load compensating snubber as in claim l in which said tirst conduit and said second conduit are connected by a pipe and in which said pipe is normally blocked by a relief valve opened by pressure in excess of a predetermined maximum pressure.

6. A hydraulic load compensating snubber as in claim 1 in which an accumulator is connected to said second conduit.

7. A hydraulic load compensating snubber as in claim l in which a bypass conduit connects said first conduit and said second conduit and in which ow from said rst conduit to said second conduit through said bypass conduit is blocked by a cheek valve.

S. A hydraulic load compensating snubber as in claim l in which said control means includes a pair of valves connected hydraulically in parallel and actuated by a pair of solenoids connected electrically in series.

9. A hydraulic load compensating snubber as in claim 1 in which said second conduit and said fourth chamber are connected through a check Valve opening toward said fourth chamber.

10. A hydraulic load compensating snubbcr for use with a member mounted to pivot on a frame about an axis comprising a hydraulic variable enclosure including a first cylinder closed at both ends and having a first piston therein dividing said rs't cylinder into a rst chamber and a second chamber and havinU a piston rod on said piston extending through one of said ends, iirst means for pivotally mounting said cylinder on said frame, second means for pivotally mounting said piston rod on said member at a point crossing a line connecting said first means and said axis as said member pivots on said frame, a control unit including a second cylinder closed at both ends and having a Wall with a plurality of openings therein andrhaving a second piston therein dividing said second cylinder into a third chamber and a fourth chamber, said piston being movable to overlie and block said openings successively, a irst conduit extending between said first chamber and said third chamber, a second conduit extending between said second chamber and said fourth chamber, a hydraulic connector between said rst conduit and said second conduit, a valve in said connector movable between one position permitting ow through said connector and another position blocking iiow through said connector, and means controlled by the position of said member relative to said frame for moving said valve between said positions.

ll. A hydraulic load compensating snubber as in claim l in which said fourth chamber and said second conduit communicate through an opening varied in area according to the position ot said second piston in said second cylinder.

References 'Cited by the Examiner UNITED STATES PATENTS 2,755,871 7/56 Gerstenberger 18S-97 2,809,722 10/57 Smith 18S-97 2,931,035 3/60 Reinhard et al. 3,930,100 4/62 Wagner. 3,106,992 lil/63 Sherburne l88-97.1

FOREIGN PATENTS 722,476 12/3l France.

ARTHUR L. LA PONT, Primary Examiner. 

1. A HYDRAULIC LOAD COMPENSATING SNUBBER COMPRISING A HYDRAULIC VARIABLE ENCLOSURE INCLUDING A FIRST CYLINDER CLOSED AT BOTH ENDS AND HAVING A FIRST PISTON THEREIN DIVIDING SAID FIRST CYLINDER INTO A FIRST CHAMBER AND A SECOND CHAMBER AND HAVING A PISTON ROD ON SAID PISTON EXTENDING THROUGH ONE OF SAID ENDS, A CONTROL UNIT INCLUDING A SECOND CYLINDER CLOSED AT BOTH ENDS AND HAVING A SECOND PISTON THEREIN DIVIDING SAID SECOND CYLINDER INTO A THIRD CHAMBER AND A FOURTH CHAMBER, A FIRST CONDUIT EXTENDING BETWEEN SAID FIRST CHAMBER AND SAID THIRD CHAMBER, A SECOND CONDUIT EXTENDING BETWEEN SAID SECOND CHAMBER AND SAID FOURTH CHAMBER, A HYDRAULIC CONNECTOR BETWEEN SAID FIRST CONDUIT AND SAID SECOND CONDUIT, A CONTROL MEANS MOVABLE BETWEEN ONE POSITION PERMITTING FLOW THROUGH SAID CONNECTOR AND ANOTHER POSITION BLOCKING FLOW THROUGH SAID CONNECTOR, AND A FLOW CONTROL VALVE IN SAID FIRST CONDUIT RESPONSIVE TO THE DIFFERENCE IN PRESSURE BETWEEN SAID THIRD CHAMBER AND SAID FOURTH CHAMBER. 